Electrochemical synthesis of three-dimensional porous networks of nickel with different micro-nano structures for the fabrication of Ni/MnOx nanocomposites with enhanced supercapacitive performance

We have electrochemically synthesized 3D-porous Ni/MnOx nanocomposites for supercapacitor applications. 3D porous micro-nanostructured networks of nickel were prepared using hydrogen bubbles as a dynamic template at different deposition potentials and times. The prepared nickel films were used then as 3D-porous substrates for anodic deposition of manganese oxide nanostructures. The effects of deposition potential and time on the structure of the prepared nickel scaffolds and especially on the capacitive behavior of the subsequently fabricated 3D-porous Ni/MnOx nanocomposites were investigated. The results show that the areal capacitance and especially the rate capability of prepared Ni/MnOx nanocomposites have improved with increasing the deposition potential or optimizing the deposition time of nickel films in the nanocomposites. The prepared 3D-porous Ni/MnOx nanocomposite, in which the nickel scaffold has been deposited at the potential of -6 V and duration of 90s, show almost the highest capacitive performance among all other prepared nanocomposites. This prepared nanocomposite, with the loading mass of 1.65 mg cm(-2), showed the high areal capacitance of 654 mF cm(-2) (396.4 F g(-1)) at the current density of 0.5 mA cm(-2) (0.3 A g(-1)) in 0.5 M Na2SO4 solution. This nanocomposite also revealed the highest rate capability; the capacitance retention is about 63% (412 mF cm(-2)) with increasing the discharge rate from 0.5 to 20 mA cm(-2), which is almost twice the observed amount of retention when the deposition potential of Ni films was -2V (31%) or their deposition time was 45 s (34%). In addition, the prepared nanocomposite exhibited an outstanding cycling stability. The capacitance retention was about 98.91% after performing 2000 charge-discharge cycles. (C) 2017 Elsevier B.V. All rights reserved.